Add Arabic translation (ar_AR)

[HuseinAlfeel]

Summary

This PR adds the first Arabic translation of the idiomatic.js style guide.

What's included

• ✅ Complete Arabic translation (translations/ar_AR/readme.md)
• ✅ Professional translation maintaining technical accuracy
• ✅ Cultural adaptation for Arabic-speaking developers
• ✅ Proper RTL text flow and Arabic typography

Why this matters

• Arabic is spoken by 400+ million people globally
• This fills a significant gap in available translations
• Makes JavaScript best practices accessible to the Arab developer community
• Follows the same high-quality standards as other translations in the project

Translation approach

• Translated from German source for better accuracy (I speak German fluently)
• Maintained English technical terms where appropriate for consistency
• Used established Arabic programming terminology
• Ensured proper Markdown formatting and GitHub compatibility

Testing

• ✅ Verified Markdown formatting renders correctly
• ✅ Checked all links and anchors work properly
• ✅ Confirmed consistent styling with other translations